FinanceCalcs
Area Calculator
Calculate the area of any shape. Select a shape, enter the dimensions, and get the area instantly with the formula shown. Supports circles, rectangles, triangles, trapezoids, parallelograms, ellipses, sectors, and regular polygons.
Area Calculator
Rectangle
Area: 0 ft²
Calculation Details
Area in Other Units
| Unit | Area |
|---|
"Archimedes calculated the area of a circle to arbitrary precision around 250 BC using the method of exhaustion — a precursor to calculus, nearly 2,000 years before Newton."
— History of Mathematics
Area formulas reference
| Shape | Formula |
|---|---|
| Circle | A = πr² |
| Rectangle | A = length × width |
| Triangle | A = ½ × base × height |
| Trapezoid | A = ½(a+b) × h |
| Parallelogram | A = base × height |
| Ellipse | A = π × a × b |
| Regular polygon | A = ¼n × s² × cot(π/n) |
Area FAQs
How do you find the area of a triangle without the height?
Use Heron’s formula: given sides a, b, c, calculate the semi-perimeter s = (a+b+c)/2, then area = √(s(s−a)(s−b)(s−c)). This works for any triangle when you know all three side lengths but not the height.
How many square feet in an acre?
Exactly 43,560 square feet per acre. An acre is also 4,047 m², 0.4047 hectares, or roughly the size of a typical American football field (minus the end zones). The hectare (10,000 m²) is the metric equivalent used in most countries.
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About FinanceCalcs.net — FinanceCalcs.net is a free financial calculator directory built and maintained by Ted Grajeda. The site exists to give everyone access to fast, accurate financial math — no subscriptions, no paywalls, no signup required. Every calculator runs entirely in your browser using standard financial formulas.